Scroll type fluid machines are well known in the conventional art, and they are utilized in various applications, such as a compressor for refrigerant compression in a refrigeration apparatus. For example, JP Patent Application Kokai Pub. No. 1997-126164 and JP Patent Application Kokai Pub. No. 2002-235682A disclose scroll type fluid machines having movable- and stationary-side wraps, wherein the movable- and stationary-side wraps are arranged in two sets and brought into engagement with each other. In such a scroll type fluid machine, both surfaces of a flat-plate part in an orbiting scroll are provided with respective spiral wraps vertically arranged. More specifically, in the scroll type fluid machine, a movable-side wrap vertically arranged on the front surface of the flat-plate part engages a first stationary-side wrap to form a first fluid chamber while on the other hand a movable-side wrap vertically arranged on the back surface of the flat-plate part engages a second stationary-side wrap to form a second fluid chamber.
In such a type of scroll type fluid machine, however, it is required that its rotating shaft be brought into engagement with an orbiting scroll having a flat-plate part both surfaces of which are provided with vertically-arranged wraps. To this end, the aforesaid publication 1997-126164 shows a technique in which a rotating shaft is disposed, such that it passes through the center of a flat-plate part in an orbiting scroll and an eccentric part of the rotating shaft is brought into engagement with the flat-plate part. On the other hand, the aforesaid publication 2002-235682 shows a technique in which an insertion part is formed, such that it passes through the center of a flat-plate part in an orbiting scroll and an eccentric part of a rotating shaft is inserted into the shaft insertion part from the back surface side of the flat-plate part.